Depending on one's perspective, Porsche does't currently have a street car engine that's been racing.

The old GT3 engine doesn't meet current emission regulations and has been retired. 

The prototype I saw back then I thought it had a GT3 4.0 in it, as I saw the GT3's 9k tech in the cockpit, but now with more information I guess it perhaps isn't and could have been a more tuned up version of the 4.0 in the new 718 GT4.

The much less restrictive air intake track would give it the needed boost in power production over the regular GT4.

Fitting the 4.0 from the Speedster in a detuned state could be an option, but the car would also cost quite a bit more. 

Regardless, the achilles heel had always been the gearbox, 2nd gear to be exact, be it the manual version or the PDK in the race car. Gutless would be the correct description of the gearing. 


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